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Topic: Martian forest (Read 19751 times)

The problem with plant products whenever I start considering them is that you can always get much more production with synthetics for a given amount of mass shipped from Earth (at least in the near term). A small UHMWPE powder production system can produce more polyethylene in an hour than the equivalent mass of hydroponics system could produce bamboo in a year.

The problem with plant products whenever I start considering them is that you can always get much more production with synthetics for a given amount of mass shipped from Earth (at least in the near term). A small UHMWPE powder production system can produce more polyethylene in an hour than the equivalent mass of hydroponics system could produce bamboo in a year.

The idea is to minimize shipping supplies from Earth by producing products at the colony.

Where does the colony get the ethylene to produce UHMWPE powder? Ethylene can be synthesised from ethanol and sulfuric acid or ethanol and aluminum oxide, but where do those come from? Ethanol is produced during fermentation via yeast and sugars. Best way to produce sugar is growing sugar beets or sugarcane, so it looks like we're back to growing plants.

And bedding (in fact, the entire bed!), towels or drapes. It can also be used for utensils like spoons and chopsticks, blinds, brushes, parasols (if you need to keep the sun off!), sinks & bathtubs, sugar (similarly to sugar cane), beverages (beer, wine & tea), beehives (if you need bees!), musical instruments (flutes and drums), rope, containers (and can be woven into baskets like rattan or reeds). If you have animals it can be used as fodder or fencing. Quite versatile stuff.

The idea is to minimize shipping supplies from Earth by producing products at the colony.

Where does the colony get the ethylene to produce UHMWPE powder?

Systems for in-situ production of UHWMPE on Mars are not theoretical, they've already been built. Ethylene is produced from the partial oxidation of methane in a microreactor cascade. It can also be produced direct from syngas.

Note that there still are consumables. For example, in a prototype Mars UHMWPE system designed for producing a UHMWPE/aggregate concrete substitute , they were using liquid phase polymerization, wherein the catalyst ends up (in tiny quantities) in the plastic. But there's also gas phase polymerization options where it doesn't. And in any system there's always going to be some consumables. Agriculture is absolutely no exception. The production rate difference, however, is massive.

There is research in an advanced stage to convert methane to ethylene. The driver for this research is the methane byproduct of oil wells. In many areas there is no infrastructure to transport the methane and it is still being burned off. Catalytic transformation of methane to ethylene can eliminate that waste. Very useful on Mars too.

There is research in an advanced stage to convert methane to ethylene. The driver for this research is the methane byproduct of oil wells. In many areas there is no infrastructure to transport the methane and it is still being burned off. Catalytic transformation of methane to ethylene can eliminate that waste. Very useful on Mars too.

Systems for in-situ production of UHWMPE on Mars are not theoretical, they've already been built. Ethylene is produced from the partial oxidation of methane in a microreactor cascade. It can also be produced direct from syngas.

Note that there still are consumables. For example, in a prototype Mars UHMWPE system designed for producing a UHMWPE/aggregate concrete substitute , they were using liquid phase polymerization, wherein the catalyst ends up (in tiny quantities) in the plastic. But there's also gas phase polymerization options where it doesn't. And in any system there's always going to be some consumables. Agriculture is absolutely no exception. The production rate difference, however, is massive.

That sounds good. Those should be mature technologies by the time they're needed on Mars.

So growing construction materials won't be needed, but it would be nice to have a small grove to make a colony more livable.

So growing construction materials won't be needed, but it would be nice to have a small grove to make a colony more livable.

Having things like chopping boards and some furniture items from bamboo would make a habitat a lot more livable, even when plastic is cheaper. Fast growing bamboo can play a major role. Paper too, think nappies.

If you have an interest in chemical processes, by the way, I strongly recommend Ullmann's Encyclopedia of Industrial Chemistry. Google it along with any random chemical to see in detail how it and all of its feedstocks are made Assuming you have access (or if not, then assuming you're willing to use sci-hub )

I guess whether to grow plants or artificially create plastics will all depend on which has the least requirements for mass shipped from Earth including required spare parts. I think it has been stated that plants will grow best under solar powered LEDs rather than natural light for the same energy input. The mass required to be shipped will be higher under LEDSs if on the surface. If we can find suitable tunnels this may not be true. How much energy is required to create a Kg of ethylene from water and the Mars atmosphere ?

I guess whether to grow plants or artificially create plastics will all depend on which has the least requirements for mass shipped from Earth including required spare parts. I think it has been stated that plants will grow best under solar powered LEDs rather than natural light for the same energy input. The mass required to be shipped will be higher under LEDSs if on the surface. If we can find suitable tunnels this may not be true. How much energy is required to create a Kg of ethylene from water and the Mars atmosphere ?

Plants are horribly inefficient converters of energy, plus even LED lights are quite wastefu, so it's compounding major losses upon major losses. Plants are generally 0.1-2% efficient at turning solar energy into stored biomass energy.. LED grow lights may end up with about 30% of their input electricity kicked off as PAR (or less). Typical solar panels are under 20% efficient, although super-expensive multijunction can get over 30%. But let's leave solar off since both routes need power; you're looking at less than 1% efficiency, potentially far less. With external power demands (climate control, water pumps, etc) to boot. So if you were to take a 0.5% efficient plant (I don't know how efficient bamboo is) and 30% efficient lights, then burned the resulting biomass, you'd get 0,15% * (thermal energy recovery efficiency) of your energy back.

For plastics: a PEM electrolyser without heat recovery can make hydrogen and oxygen for ~60% efficiency; alkaline, more like 50%. These numbers are rising. All other reactions (sabatier synthesis, methane oxidation to ethylene, ethylene polymerization) are exothermic; they don't need additional energy input. They're also highly selective (aka, only small amounts of non-target products that need to be regassified). So if you burned the polyethylene, and combined that with the heat given off of the production reactions, you'd get 50-60% * (thermal energy recovery efficiency) of your energy back. Even better, actually, because you could also use waste heat from the electrolysis itself. It might be tempting to say "Well, what about the plants' losses, why can't you recover them thermally?" - except that because plant metabolism is so slow, they never result in the plant reaching temperatures significantly different from ambient, so there's no meaningful efficiency for recovery under Carnot's law.

"According to Ford, bamboo performed significantly better than other synthetic and natural materials when subjected to both tensile strength and impact strength tests. In its pure, natural form, however, it can't be molded into specific shapes. That's why the automaker has combined bamboo fibers with plastic, to form a composite known as Bamboo 2."

With the availability of cheap polythene and similar mentioned above we can mass produce domes to grow our forest...

Yes, I believe we can expect to see bamboo and plant life like bamboo in the mid years of the Mars missions due to it's limitless usefulness. Any plant life would put us as humans well on our way to colonization.

Plastic made from sugar and carbon dioxide>The new BPA-free plastic could potentially replace current polycarbonates in items such as baby bottles and food containers, and since the plastic is bio-compatible, it could also be used for medical implants or as scaffolds for growing tissues or organs for transplant.>"The properties of this new plastic can be fine-tuned by tweaking the chemical structure -- for example we can make the plastic positively charged so that cells can stick to it, making it useful as a scaffold for tissue engineering." Such tissue engineering work has already started in collaboration with Dr Ram Sharma from Chemical Engineering, also part of the CSCT.>